The 3-D Flow Field Numerical Simulation Of Kaplan Turbine Based On Weak-Coupling

Through the internal flow analysis of the Kaplan turbine components, in-depth studies of the connection between the turbine structure and the flow field, it had great significance for improving the comprehensive hydraulic turbine performance, design standards and the operational stability of hydraulic unit.In this paper, we used CFD technology to make three dimensional steady and unsteady flows numerical simulation in the whole passage of Kaplan turbine, in considering guide vanes stretches out the ring at the end there on the cusp gap circumstances turbine performance impact. In this paper, the work was as following:(1) Based on the analysis of flow mechanism, the numerical simulation of the period guide vane and the period runner of the Kaplan turbine were conducted by using Reynolds averaged N-S equation and k -εturbulence model with double equation. It had analyzed the flow characteristics and hydraulic performance in the consideration of guide vane stretches out bottom ring existence acute angle gap in the situation. It was pointed out that in the guide vane big opening's situation, the acute angle gap place had obvious tip clearance vortex, it provided the reference for further discussing to how to establish the accurate geometric model combined with experiments.(2) In this paper, we established model and carried on calculation of the 3-D with the steady flow in entire flow channel, including the spiral case, stay vanes, guide vanes, runner and draft tube based on the CAD technology. It caught the important mobile information of the Kaplan turbine, such as interior pressure field, the field of velocities and so on. We obtained that the speed moment in the entire spiral case internal distribution and the design theory with V_uR = constant was consistent. Through the comparison of the stay vane setting angle with the fluent import angle, it provided advisory opinion for guide vane's arrangement design and the runner three-dimensional flow computation. Through the further comparison of the pressure and the speed changed when the runner blade revolved different position, it provided the basis for the further strength calculation.(3) As the CFD simulation calculation of the single-flow turbine flow or individual components as of the flow didn't consider the coupling interference of components, so the forecast had bigger difference in results. In this paper, the pressure fluctuation capability of Kaplan turbine under the FSI of the runner's blades was forecasted based on the steady calculation and characters of flow in runner and draft tube were analyzed.